I'm not a huge fan of Juma as a ferrule material for break cues, but it's usually fine for joint and shaft collars. It's a thermoset material it's it not anywhere near as strong as phenolic or LBM type materials. @TeddyKGB you mention you cue only has a joint collar and the shaft has no shaft collar and it's a big pin cue, to me that's more of an issue..
Could be, just got the impression that the shaft had no collarJust a different take here, he didn't say that the shaft had no collar, just that the juma was on the butt. There could be another collar of another material on the shaft and below the juma on the butt.